如何单独使用 Rails 的路由系统

forum_markdown.rb

# test for Rails 4.1.9
# file: app/models/forum_markdown.rb
class ForumMarkdown

  class DummyController
    def logger
      RAILS_DEFAULT_LOGGER
    end

    def headers
      {}
    end

    def _prefixes
    end
  end

  def self.render(options, assigns = {})
    viewer = ActionView::Base.new(File.join(Rails.root, 'app/views'), assigns, DummyController.new)
    helper = Rails.application.routes.url_helpers
    if options[:locals]
      options[:locals][:helper] =  helper
    end
    viewer.render options
  end
end

main.rb

ForumMarkdown.render file: 'xx.md.erb', locals: { video_course: video_course }

xx.md.erb

# <%= video_course.name %>

![](<%= helper.root_url + ActionController::Base.helpers.asset_path(video_course.cover_url) %>)

## 课程介绍

<%= video_course.description %>

更多请点击: [课程详情](<%= helper.video_course_url(video_course) %>)